avoid polluting the default geth directory

 * this caused test failures for other tests which used geth on the
   default directory and the mainnet chain id

ethers-core/src/utils/geth.rs

@@ -2,7 +2,7 @@ use super::{unused_port, Genesis};
 use crate::types::H256;
 use std::{
     env::temp_dir,
-    fs::File,
+    fs::{create_dir, File},
     io::{BufRead, BufReader},
     path::PathBuf,
     process::{Child, Command, Stdio},
@@ -324,6 +324,11 @@ impl Geth {
 
         if let Some(ref data_dir) = self.data_dir {
             cmd.arg("--datadir").arg(data_dir);
+
+            // create the directory if it doesn't exist
+            if !data_dir.exists() {
+                create_dir(data_dir).expect("could not create data dir");
+            }
         }
 
         // Dev mode with custom block time

ethers-providers/src/provider.rs

@@ -2176,13 +2176,14 @@ mod tests {
         let p2p_listener_port = 13337u16;
         let authrpc_port = 8551u16;
         let network = 1337u64;
+        let temp_dir = tempfile::tempdir().unwrap().into_path();
 
         let (geth, provider) = spawn_geth_and_create_provider(
             network,
             port,
             p2p_listener_port,
             authrpc_port,
-            None,
+            Some(temp_dir),
             None,
         );